1. Field of the Invention
The present invention relates to a semiconductor wafer treatment member consisting of only a silicon carbide (SiC film) film thereon, or on the surface of the substrate having a silicon carbide film thereon, in other words, at least on the surface thereof and more particularly to a semiconductor wafer treatment member used as components in a jig for treating semiconductors such as wafer boards, susceptors, etc.
2. Description of the Related Art
In the process of the semiconductor manufacturing, it is a widely followed procedure to form a silicon nitride (Si3N4) or poly silicon thin film on the surface of semiconductor wafer. As a jig used to work on wafer boards for such thin film forming process, a quartz glass jig, or a jig having only a silicon carbide (SiC) film or a silicon carbide (SiC) film formed on carbon-impregnated, SiC-impregnated or SiC surfaces is used.
Such jigs composed of a semiconductor wafer treatment member having a SiC film formed on at least the surface thereof are widely used in CVD devices operated at a high temperature because of their better heat resistance cycle characteristics, better thermal shock resistance as compared to the quartz glass jig.
The film forming methods for obtaining a semiconductor wafer treatment member having a silicon carbide (SiC) film thereon on the surface thereof include (1) a method in which raw material gases of silicon and carbon origins are introduced into the reactor from outside to be heated at a normal pressure or a reduced pressure; or (2) a method in which, for the substrate being made of carbon, a raw material gas of silicon origin is introduced into the reactor from outside to be heated at a normal pressure or a reduced pressure.
The silicon carbide (SiC) film formed by chemical vapor deposition as discussed above is formed with serrations in the surface thereof. Although random in size, said serrations are formed of part of sharp crystal grains. FIGS. 4 and 5 provide general views thereof; FIG. 4 is an explanatory plan view and FIG. 5 is an explanatory view in cross section of the surface thereof. It is to be noted that the black areas show depressions while the white areas show salients.
In FIG. 5, the character B denotes a substrate of for example carbon with a CVD silicon carbide (SiC) film C. Further, said silicon carbide (SiC) film has salients 1 formed with serrations having sharp edges 1 which are part of crystal grains.
When the semiconductor wafer treatment member having this surface as described above is used for semiconductor wafer manufacturing, the serrations having sharp salients 1 generate mechanical or thermal stresses to cause the semiconductor wafer to be flawed or slippery.
In order to solve this problem, the (top) surface of the silicon carbide film (SiC film) is subjected to grinding on the machine platen after formation of the silicon carbide film to remove said edges of the serrations and obtain a mirror surface. The explanatory view of an obtained surface is shown in FIG. 6, which is a cross section to show the surface state thereof.
In this way, the silicon carbide (SiC) film polished into a mirror surface shows a strong contact characteristic to such an extent that the semiconductor wafer adheres to the silicon carbide film to give rise to a problem that the semiconductor wafer adheres to the silicon carbide when the semiconductor wafer placed there is to be taken out. Therefore, the semiconductor wafer is subjected to blasting after the grinding operation in order to have an optimum cohesion characteristic against the semiconductor wafer. In order to realize this purpose, the optimum irregularities are formed after the mirror surface grinding.
It is to be noted that said silicon carbide (SiC) film polished into a mirror surface undergoes mechanical external force at the entire surface thereof due to the grinding on the machine platen.
Further, the silicon carbide (SiC) film subjected to blasting after the mirror grinding to form an optimum irregularities receives a mechanical external force at the entire surface thereof.
The surface of the silicon carbide (SiC) undergoing such mechanical force from outside has minute microcracks especially in the grain boundary of the SiC crystal as well as damaged portions unobservable by visual check. Consequently, if the semiconductor wafer is subjected to the dry washing by oxygen baking or the like or the wet washing by hydrogen fluoride (HF) or the like prior or subsequently to the semiconductor wafer treatment, the degradation of said silicon carbide (SiC) film starts from said microcracks or cracks accompanying the growth of the damage, providing contributing factors of shortening of the service life of the semiconductor treatment member. Further, such cracks, once formed, give rise to problems that the substrate emits gases containing impurities such as carbon monoxide or carbon hydride, contaminating the semiconductor wafer to be treated.